This invention relates generally to wind turbine generators, and more particularly, to methods and apparatus for cooling wind turbine generators.
Recently, wind turbines have received increased attention as an environmentally safe and relatively inexpensive alternative energy source. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.
Generally, a wind turbine includes a plurality of blades coupled to a rotor through a hub. The rotor is mounted within a housing or nacelle, which is positioned on top of a tubular tower or base. Utility grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., 30 or more meters in diameter). Blades on these rotors transform wind energy into a rotational torque or force that drives the rotor of one or more generators, rotationally coupled to the rotor. The rotor is supported by the tower through a bearing that includes a fixed portion coupled to a rotatable portion. The bearing is subject to a plurality of loads including a weight of the rotor, a moment load of the rotor that is cantilevered from the bearing, asymmetric loads, such as, horizontal wind shears, yaw misalignment, and natural turbulence
In the generator, rotor components and stator components are separated by an airgap. During operation, a magnetic field generated by permanent magnets and/or wound poles mounted on the rotor passes through the airgap between the rotor and the stator. The stator includes a core and a coil surrounding the core. The magnets induce a current in the core and coil to generate electricity.
However, when the electricity is generated in the core and coil, the core and coil generate a significant amount of heat. Heat is also generated in the rotor and the magnets. Conventional cooling systems for the generator components include air cooled ventilation systems and water cooled systems. These conventional systems are typically complex and require additional components to facilitate cooling. Additionally, these conventional systems require maintenance and power to operate. These factors add cost to the operation of the generator.